Good tutorial, the only thing I can add as a suggestion to others is that you should be careful when using photo ref and then using a program like Crazybump or Nvidia's Normal Map Filter. Often photographs, (if not taken under proper conditions) will have shadows that will contribute to the depth of a normal map which really isn't there. Here's a few tutorials that talk about these issues more at length.
djsnug76
Jonathan joined
Video Game Artist - Environment Modeler and Texture Artist.